Description

▲

The oligotrophic Kejimkujik Lake in Kejimkujik National Park is lying on Devonian granite in central Nova Scotia approximately 60 km inland from the Atlantic Ocean and 40 km from the Bay of Fundy. Its drainage basin is covered by forest, bogs, lakes and a very limited amount of poor agricultural land (<1% of the watershed). About two-thirds of the drainage basin is outside of the National Park boundary which contains a permanent population of <100 people, has some roads and supports some forestry and a very limited amount of agriculture. Kejimkujik Lake is a local centre of summer recreation. Up to ca. 1,500-2,500 people may be present daily during peak periods of the summer season. Water flowing into the lake is influenced by bog soils and is high in organic acids. The lake has shown a high degree of acidification and reproductive failure of Atlantic salmon due to high acidity downstream from the lake has become apparent.

In response to the need for scientific knowledge of the potential impacts of the long-range transportation of air pollutants on freshwater ecosystems in Atlantic Canada, the Government of Canada initiated the Kejimkujik Calibrated Catchment Study Program, an interdisciplinary multi-agency study in 1980.

The lake is shallow and has a relatively high flushing rate (4.5 times yr-1), precipitation is 1,460 mm yr-1 and the runoff is 910 mm yr-1. The water is extremely dilute (sum of constituents = 13 mg l-1), and due to its relative closeness to the ocean, it is dominated by Na and Cl ions. Calcium and magnesium concentrations are extremely low (0.7 and 0.5 mg l-1, respectively); thus under the existing ca. 20 kg ha-1 yr-1 wet sulphate deposition, combined with the existing natural acidity, the lake responds with chronically depressed pH (4.8 annual mean). Studies in the lake and its tributaries showed that the additional sulphate deposition of anthropogenic origin gives additional acidity to the water, particularly during the winter and early spring, which explains the disappearance of Atlantic salmon downstream from the lake (Q).